GM Module timing curves

[1BadAction]

So we don't completely hijack the other thread.

There was some testing done on Thirdgen.org that proved even 2 differant numbered GM modules have differant timing curves. I furthered the testing and can guarantee that you never know what timing will be at any RPM with aftermarket modules...

So you're saying that 24 degrees commanded might not necessarily = 24 degrees? Is this why all these timing curves look weak on the "mechanical" side?

My 90kpa @2800RPM is 20 degrees in the tune, with no adders active, but it could actually be higher (or lower?)

[EagleMark]

Yup! Never know... even the spark latency settings in all stock GM bins are not accurate. I think the engineers used it as a cheat? Some engines with same distributor have different settings, although same parts.

If you want a information overload then read where it was found and some testing done back in 2008 at ThirdGen.org

http://www.thirdgen.org/techboard/di...ncy-table.html

[1BadAction]

I actually added that spark latency table in the XDF for the 7060, wasn't quite sure what it did but figured it had something to do with this and may possibly be useful... Thanks for the link, I'll read up.

[1BadAction]

Interesting... Two of the exact same engines, same ECM, same mask, but totally different settings here.

BAMY 454ss based tune - 1991


BAMT 454 R/V 2500 454 tune - 1991


Probably a reason these guys have detonation issues dumping a SA table into a HD tune from a 1/2 ton 454ss tune, that is, along with the massive amount of EGR spark the HD tunes have compared.

[1BadAction]

ACDELCO D1943A is the latest part number for the 369 module, and it sounds like I may have a the 048, which explains why this thing wants so much timing in my 2800+ range.

[jim_in_dorris]

1BadAction. Another thing to consider is that the California vs Federal spark tables are totally different due to california smog rules. Perhaps one of those BCC's was a California BCC.

[Fast355]

1BadAction. Another thing to consider is that the California vs Federal spark tables are totally different due to california smog rules. Perhaps one of those BCC's was a California BCC.

Yep california bins are usually richer, have less timing, and have AIR injection.

[damanx]

Well, now that I have a new 350mhz dual time base scope, I might be able to look at some signals when I can make the time, and, after the spare ecm shows up. (Don't want to be destroying the only ECM at the moment.)

And, this spark latency is something that I think has been giving me a little grief on my tuning.

[notime2d8]

Any more info on this...? I bought one of the cheap Ebay distributors with a unidentified module...i'm thinking i should replace it.

[jdarg]

The *only* to know its correct is to try to map out the timing vs. RPM at the crank w/ a light and correct it in the latency table. I don't think mine was > 2-3 degrees out though and that was only in a couple of spots so depending on your goals (this is a Jeep and I'm not concerned with ETAs) it might be splitting hairs.

[chevmasta]

So we don't completely hijack the other thread.


So you're saying that 24 degrees commanded might not necessarily = 24 degrees? Is this why all these timing curves look weak on the "mechanical" side?

My 90kpa @2800RPM is 20 degrees in the tune, with no adders active, but it could actually be higher (or lower?)

FWIW, my current tune has 22* at the same load and RPM.....but I'm waaaay less efficient than your engine. lol

Yup! Never know... even the spark latency settings in all stock GM bins are not accurate. I think the engineers used it as a cheat? Some engines with same distributor have different settings, although same parts.

If you want a information overload then read where it was found and some testing done back in 2008 at ThirdGen.org

http://www.thirdgen.org/techboard/di...ncy-table.html

I have the DUI setup....full distributor and coil. I remember at some point reading that the DUI modules were extremely good. Similar to the 369 modules I believe.

[EagleMark]

I have the DUI setup....full distributor and coil. I remember at some point reading that the DUI modules were extremely good. Similar to the 369 modules I believe.

Well if you read it on the internet then it must be true?

But as shown above here the same engine etc... has different latency's! So GM must have used this as an adjustment? Most of them are really close, say at 2000 RPM but they do move timing around a few degrees, but that same number in Usec at say 5500 RPM can be off by 11*so if you really need say 22 at a certain RPM for cruise and MPG or towing then the only way to be sure is some testing with a timing light on the balancer.

[chevmasta]

Well if you read it on the internet then it must be true?

But as shown above here the same engine etc... has different latency's! So GM must have used this as an adjustment? Most of them are really close, say at 2000 RPM but they do move timing around a few degrees, but that same number in Usec at say 5500 RPM can be off by 11*so if you really need say 22 at a certain RPM for cruise and MPG or towing then the only way to be sure is some testing with a timing light on the balancer.

Haha I know! Gotta love the net! I thought I remembered reading a comparison of oscilloscopes from the dui and Delco modules. Don't remember where.

I definitely learned something today on these modules. But it's not gonna change the way I tune.

[damanx]

Yup! Never know... even the spark latency settings in all stock GM bins are not accurate. I think the engineers used it as a cheat? Some engines with same distributor have different settings, although same parts.

If you want a information overload then read where it was found and some testing done back in 2008 at ThirdGen.org

http://www.thirdgen.org/techboard/di...ncy-table.html

I just made a brief run through on that thread and I'll have to read it several more times to wrap my head around the details better, but for the mean time, I got the jist of it.

Seems this topic has come up several times in the past 6 months or so with one thread started by me I think.

What brought my attention to it was that at the time of asking the question, it was due to the fact that I was using a timing analyzer in conjunction with the spark advance hack for the 7747 ecm and was seeing two different values. I have several different timing analyzers, two digital, (one Kal-Equip and one All-Test), and one analog made by Kal-Equip. The analog is far more faster in response than the digital analyzers, but it only works with a 10 degree initial advance where the digitals and be set for the base advance. Interestingly, the Kal digital and be adjusted by single degrees for the advance all the way to 90.

In any case, the difference in the spark advance that TunerPro was showing and the advance that the timing analyzers were showing led me to the latency tables. I then found that 2.8 bins were all the same, but there was not a 2.8 bin made for the 7747 ECM. (I could be wrong on that.)

The 4.3 bin that I used for a short time had different latency values and that through a wrench into everything I thought about because it did not make sense that if the 2.8's and 4.3's commonly shared the same ignition system, why the difference. The only conclusion I could think of could have beed the crank angles being different. 60 degrees vs 90.

But I don't know for sure.

I just found out that a friend was once an engineer for GM in the anti-lock dept and thought to ask him.

His response was pretty much inline with what is posted in that thread on 3rd gen, with the addition of the fact that they sometimes wrote shit up in the programming that was not necessary. Slew rates of components, charge times, different types of pickups.....yada yada........I pretty much got the idea that it's possible they cobbled crap together to meet specs regardless of whether or not it was correct, but just as long as it worked.

In any case, I have several o'scopes and the timing analyzers. If there is any interest in seeing waveforms, I'll do it. Hell, I may just do it just because it might help me understand it better.

[Nasty-Z]

Haha I know! Gotta love the net! I thought I remembered reading a comparison of oscilloscopes from the dui and Delco modules. Don't remember where.

I definitely learned something today on these modules. But it's not gonna change the way I tune.

THe DUI Dynamod for the GM distributor is one of the best . I always try to use the 369 module but my NOS stock is fading fast , the new modules you get from GM with the new part might or might not be the genuine 369 like before , there are no markings on the ones I have ordered , just the new part # .

Only way to know for sure is to install it and try it I suppose .

TOM